Through early June, Trevor Bauer was 5-2 in 11 starts, with a 2.94 ERA that had some talking him up as a potential All-Star. In his final six starts before the break though, he gave up home runs twice as frequently as he had earlier in the year, and gave up runs at nearly double his earlier rate too. His first-half numbers still represented an upgrade over what he'd done in 2014 though; he looked like a young pitcher figuring some things out, and showing some improvement.
The second half has been a different story though. In the second half so far, Bauer has been the worst pitcher in the American League. Bauer's ERA since the break is 7.05, his FIP since the break is 6.40, highest among all qualified AL starters. FanGraphs has him down for -0.5 WAR in the second half, worst in the league.
Bauer had a couple good starts in there, including a complete game against the Royals, but he's allowed 5 or 6 earned runs in four of his seven appearances since the break. His strikeout and walk rates haven't been much different than they were before, but Bauer has been terrorized by the long ball, having given up 11 home runs in 37 innings (almost as many as the 13 Corey Kluber has given up all season, in 180.2 innings), which works out to 2.68 per 9 innings.
For the season, Bauer has a slightly higher strikeout rate than he had in 2014, and a slightly higher walk rate. He has a much higher home run rate, a home run rate so high it makes it nearly impossible to be league average as a starter. (Only two starters from 2011-2014 years reached 2 WAR for a season in which they had a HR/9 as high as Bauer's current 1.45.)
Bauer's ERA and FIP are both roughly half a run higher than they were a year ago, and his numbers would look worse if his BABIP allowed weren't 38 points lower than it was last season (Even since the All-Star break, when he's struggled so much, his BABIP allowed has been a little lower than it was a year ago.) His fastball has never been a very effective pitch for him at the Major League level, and his menagerie of off-speed pitches haven't come together consistently enough to offset the damage done against that fastball.
Unless Bauer turns things around during the final quarter of the season, it's going to be very hard to argue he's made strides this season that have improved his performance. He's still only 24, so there's certainly still time (and I have no doubt Bauer will work hard to try and find solutions), but he doesn't look any more like a front-of-the-rotation starter than he did a year or two ago. Because the Indians have Kluber, Carlos Carrasco, and Danny Salazar, there's a fair case that Bauer doesn't need to be a front-of-the-rotation starter, but on the whole, Bauer has looked like a #5 guy this season, which would be a disappointing outcome for a player drafted #3 overall.